You only can't panic knife them if they're further away from you. But that's sorta the point of Commando, right?
And the sacrificing argument does work. You're ignoring the massive benefits of other perks because you don't notice them because they're passive. You don't activate them like you do Commando; they're always active.
The shotgun thing is a connection or aim issue. Hell, even random spread can hurt the shotguns against Commando. I've had it happen to me. Yes, it is annoying. No, it's not broken. For every time you get a stupid death to Commando, they're probably being killed twice by a claymore, or a person with heartbeat, or a person with a good headset.
Everyone's problem is that the only notice their deaths due to a blatant Commando knife lunge, not the amount of times they've killed the poor Commando user for using an inferior perk to SitRep and Ninja.